/Engine/Source/Runtime/ImageCore/Public/ImageParallelFor.h
FImageis tight packed in memory with slices adjacent to each other so we can just treat it was a 2d image with Height *= NumSlices
namespace FImageCore { int32 FImageCore::ImageParallelForComputeNumJobs ( const [FImageView](API\Runtime\ImageCore\FImageView) & Image, int64 * pRowsPerJob ) }